The present invention relates to a process and apparatus for the production of foam in a continuous foam process, in particular for the production of polyurethane foam.
The product quality of foams depends on a plurality of environment and plant-related parameters. This is true in particular of the production of polyurethane foam.
Various computer-assisted processes for quality assurance in polyurethane foam production have become known. Such processes are described, for example, in “Software to Manage a Continuous Production of Flexible Polyurethane Foams by Slabstock Technology”, Salvatore Consoli, Journal of CELLULAR PLASTICS, Volume 33, March 1997, page 102, “Foam Roadmap On-line Answernostics”, James D. Shoup, Polyurethane 1995, Sep. 26-29, 1995, pages 489, 490 and “Mathematical Property Prediction Models for Flexible Polyurethane Foams”, Reinhart Schiffauer, Adv. Urethane Sci. Techn. 14 (1998), pages 1 to 44.
Expert systems for the processing of process parameters in RIM processing are also known from “Experten mit System, Prozesssteuerung des PUR-RRIM-Verfahrens zur Herstellung von KarosserieauBenteilen”, F. Schnabel, K.-H. Dörner, Kunststoffe, issue 88, 10/98 and “PUR-Teile kostengünstig fertigen, Stand der Polyurethan-RRIM-Technologie”, Karl-Heinz Dörner, Hans Joachim Meiners, Hans-Joachim Ludwig, Kunststoffe, issue 91, April 2001. Such expert systems are intended to be able to give information regarding product properties, process monitoring, quality assurance and preventive maintenance.
In addition, DE 28 19 709 B1 describes a process for the continuous production of foam sheets provided with cover layers, in which the thickness of the foam is detected in the intake cross-section by means of ultrasound, transversely to the feed direction. The manufacturing plant is then controlled via the conveyor belt speed and/or the amount of foam applied. The aim is to distribute the foam as uniformly as possible and accordingly achieve uniform foam quality.
DE 196 16 643 C1 describes a process in which, in a plant for the continuous production of foam sheets provided with cover layers, the distance between a fixed point and the edge of the foaming reaction mixture is measured by means of a laser measuring-device. In order to control the quality of the foam sheets, the actual distance value is compared with a foam-dependent desired value. The working speed of the plant is controlled according to the difference between the actual value and the desired value.
DE 199 58 689 A1 describes a process in which the surface of a discontinuously produced foam is recorded by means of a camera. The rise curve of the foam is determined from the recorded data, which in turn gives information about the reaction kinetics of the reaction mixture.
For a continuous slabstock process, DE 102 37 005 A1 describes a process in which defects in the foam due to the chemical kinetics of the foaming process are minimized by continuous detection of the actual rise heights of the foam along the conveyor device. Differences between the actual rise heights and given desired rise heights are corrected by determining a correcting variable which is used to control the slabstock process. While the aim of the process is to achieve a manufacturing process that is as uniform as possible, and hence uniform foam quality, this process does not address the issues presented by wrong settings of the production equipment.
Various processes and plant types for the production of polyurethane slabstock foam and other foams are also known from the prior art. Examples of commercially available apparatus for producing polyurethane slabstock foam are those which are sold under the names Planibloc, Draka-Petzetakis, Maxfoam, Vertifoam Edge Control and VPF processes, as well as UBT and QFM plants.
Various devices for the continuous production of polyurethane foam blocks are also known from DE 691 19 244 T2 and U.S. Pat. No. 4,492,664 A. Another device for the production of polyurethane foam is known from DE 696 10 885 T2. Various processes for the production of polyurethane foams with such apparatus are disclosed in DE 38 19 940 A1, DE 196 49 829 A1, DE 43 15 874 A1 and DE 195 06 671 C2.